Such mobile telephones mentioned above are generally referred to is known as a “slider” mobile telephone, wherein the first and the second housing part can be displaced with respect to one another in the longitudinal direction of the mobile telephone. During this displacement, a keypad is exposed which allows a user of the mobile telephone to operate it. The keypad is usually located on the housing part of the mobile telephone which is at the rear in relation to the user. The front housing part of the mobile telephone has a fixed rear wall which has no function other than that of mechanically protecting the interior of the front housing part.
Mobile phones known in the art may also be equipped with a bending wave loudspeaker. In this case, a protective window over a display device of the mobile telephone, for example, is designed as a bending wave loudspeaker and is excited to produce bending vibrations by means of a piezo operating element. Since, in addition to its function as a bending wave loudspeaker, the protective window also has to assume the functions of mechanically protecting the interior of the mobile telephone and has to be transparent, the selection of materials for the protective window is limited and cannot be optimized, in particular for the function of the protective window as a bending wave loudspeaker.